Lower Specific Growth Rate Research Articles

Quantitative physiology and biomass composition of Cyberlindnera jadinii in ethanol-grown cultures

BackgroundElimination of greenhouse gas emissions in industrial biotechnology requires replacement of carbohydrates by alternative carbon substrates, produced from CO2 and waste streams. Ethanol is already industrially produced from agricultural residues and waste gas and is miscible with water, self-sterilizing and energy-dense. The yeast C. jadinii can grow on ethanol and has a history in the production of single-cell protein (SCP) for feed and food applications. To address a knowledge gap in quantitative physiology of C. jadinii during growth on ethanol, this study investigates growth kinetics, growth energetics, nutritional requirements, and biomass composition of C. jadinii strains in batch, chemostat and fed-batch cultures.ResultsIn aerobic, ethanol-limited chemostat cultures, C. jadinii CBS 621 exhibited a maximum biomass yield on ethanol (YX/Smax) of 0.83 gbiomass (gethanol)−1 and an estimated maintenance requirement for ATP (mATP) of 2.7 mmolATP (gbiomass)−1 h−1. Even at specific growth rates below 0.05 h−1, a stable protein content of approximately 0.54 gprotein (gbiomass)−1 was observed. At low specific growth rates, up to 17% of the proteome consisted of alcohol dehydrogenase proteins, followed by aldehyde dehydrogenases and acetyl-CoA synthetase. Of 13 C. jadinii strains evaluated, 11 displayed fast growth on ethanol (μmax > 0.4 h−1) in mineral medium without vitamins, and CBS 621 was found to be a thiamine auxotroph. The prototrophic strain C. jadinii CBS 5947 was grown on an inorganic salts medium in fed-batch cultures (10-L scale) fed with pure ethanol. Biomass concentrations in these cultures increased up to 100 gbiomass (kgbroth)−1, with a biomass yield of 0.65 gbiomass (gethanol)−1. Model-based simulation, based on quantitative parameters determined in chemostat cultures, adequately predicted biomass production. A different protein content of chemostat- and fed-batch-grown biomass (54 and 42%, respectively) may reflect the more dynamic conditions in fed-batch cultures.ConclusionsAnalysis of ethanol-grown batch, chemostat and fed-batch cultures provided a quantitative physiology baseline for fundamental and applied research on C. jadinii. Its high maximum growth rate, high energetic efficiency of ethanol dissimilation, simple nutritional requirements and high protein content, make C. jadinii a highly interesting platform for production of SCP and other products from ethanol.

Impacts of alfalfa nutrient concentrate on pellet physical attributes, growth performance, metabolism and nutritional quality of rainbow trout, Oncorhynchus mykiss

This study addresses the escalating demand for aquatic feed by exploring the potential of alfalfa nutrient concentrate (ANC) as feed ingredient for rainbow trout. Test diets contained varying ANC levels (0%, 5%, 10%, 15%, and 20%) to replace fishmeal (32% in the 0% ANC diet) to achieve equal digestible protein and were processed using a cooking extrusion method. Analysis of feed pellets showed that pellet density increased with ANC levels (P < 0.001), resulting in sinking pellets at 20% ANC. Water stability and durability were improved while oil leakage decreased with increasing ANC levels (P < 0.05). Two feeding trials were conducted to test the diets in flow-through water systems with three replicates per diet. The first 10-week trial evaluated their impact on feeding, fecal physical quality, and the apparent digestibility coefficient (ADC) of dietary nutrients in rainbow trout (initial body weight , 18.0 ± 0.2 g). ANC inclusion did not impact the palatability and satiety feed intake of the fish (P > 0.05). However, the ADC of dry matter and phosphorus significantly decreased in fish fed the 20% ANC diet (P < 0.05). The second 9-week trial investigated the growth performance, nutrition quality, and metabolism of rainbow trout (initial body weight, 19.0 ± 0.2 g). While all fish exhibited substantial growth, fish fed diets with 10% to 20% ANC displayed lower specific growth rate and higher feed conversion ratio compared to those fed with 0% or 5% ANC (P < 0.05). The whole body protein content was higher in fish fed 5% ANC compared to all other treatments (P = 0.030). The biochemical parameters of plasma were similar across treatments, except for a decrease in plasma phosphorus levels in fish fed a 10% ANC diet compared to those fed a 0% ANC diet. (P = 0.033). Significant changes were observed in liver metabolism including tricarboxylic acid cycle, amino acid and energy metabolism pathways in fish fed the 20% ANC diet versus the 0% ANC diet (P < 0.05). These results demonstrate that ANC inclusion improved pellet physical quality without impairing feeding behavior and nutritional quality of the fish but inclusion ≥10% in the diet reduced fish growth. This study offers the first comprehensive assessment of the potential of ANC used in fish feed involving feed management, feeding evaluation, and the biological response.

Biomass Productivity and Photosynthetic Activity in Ulva compressa (Chlorophyta) in Raceway Photobioreactors Under Stress Conditions.

Research in seaweed cultivation technologies aims to increase production and reduce costs, leading to more efficient and sustainable processes. In this study, we analyzed the outdoor production of Ulva compressa cultured in summertime at different stocking densities of 0.6, 0.8 and 1.0 kg Fresh weight (FW) m-2 in a raceway photobioreactor with 30 m2 surface (3000 L), and its relation to photosynthetic activity. Under the experimental conditions of high temperature (>28-30 °C) and pH > 9 in culture water, higher seaweed density resulted in lower specific growth rate. The biomass production has been related to photosynthetic activity by using in vivo chlorophyll a fluorescence. Dynamic photoinhibition was observed at noon, which was less severe in cultures with higher algal densities. However, photosynthesis recovered in the afternoon. Seaweeds that were acclimatized for a week to the conditions of 1.0 kg FW m-2 stocking density showed an increase in biomass growth and absence of photoinhibition compared to non-acclimatized thalli. In conclusion, the cultivation of U. compressa in a mid-scale raceway photobiorreactor under conditions of high irradiance and temperature and low nutrient input, exhibited the best photosynthetic performance and hence the highest growth rates for the highest culture density assayed (1.0 kg FW m-2).

Evaluation of Nymphaea nouchali leaf meal based diets on growth, digestive enzymes and haematological parameters of Labeo catla fingerlings (Hamilton, 1822)

Aim: This study was conducted to evaluate the nutraceutical traits of Nymphaea nouchali herbal plant ingredients on the growth performance, digestive enzymes and health status of Labeo catla fingerlings owing to the abundance of phytoconstituents. Methodology: Four isonitrogenous and isocaloric diet with different inclusion levels of Nymphaea nouchali leaf meal (NNLM) i.e., 0%, 20%, 30% and 40% were formulated and designated as T-0, T-I, T-II and T-III treatment groups. A total of 144 fingerlings of L. catla were randomly distributed into the experimental cisterns in triplicates following completely randomized design. Results: At the end of the experiment, the percent weight gain and specific growth rate (SGR) were significantly higher (P&lt;0.05) with significantly lower (P&lt;0.05) feed conversion ratio (FCR) in T-II group as compared to the other experimental groups. Significantly lower (P&lt;0.05) percent weight gain and SGR with significantly higher (P&lt;0.05) FCR were recorded in T-0 and T-III. The protease and amylase activities were found to be significantly higher (P&lt;0.05) in the T-II with lower (P&lt;0.05) values recorded in T-0 and T-III groups. The red blood cell count and haemoglobin level were found to be significantly higher (P&lt;0.05) in the T-I and T-II groups as compared to T-0 and T-III, respectively. Interpretation: The present study demonstrated that dietary inclusion of Nymphaea nouchali leaf meal with 30% improved growth, nutrient utilization and better health benefits of L. catla fingerlings in the present culture condition. Key words: Digestive enzymes, Herbal plant, Labeo catla, Leaf meal, Nymphaea nouchali

Comparative impact of replacing fish meal with azolla on growth, water quality, and physiology of red tilapia fingerlings at varying salinities.

A 210-day experiment to assess the efficacy of substituting azolla plant powder at levels of 0, 20, 40, and 60% for fish meal on red tilapia fingerlings (RTF, initial weight of 18.23 ± 0.12 g) performance under salinity levels of 5, 18, and 28ppt. Among the various conditions, RTF-fed 20% azolla at 28 and 5ppt salinity showcased the highest specific growth rate (SGR), whereas the lowest SGR was observed in fish-fed 60% azolla at 5ppt salinity. Upon azolla incorporation, noteworthy elevations in phytoplankton, zooplankton, dissolved oxygen (DO), pH, NH3, and NO3 were noted and conversely, azolla introduction led to decreased NH4 and NO2 concentrations in all salinity levels. Further, a significant (p < 0.05) interaction between azolla levels and water salinity (S×A) significantly impacted the hematological parameters of RTF. The highest levels of superoxide dismutase (SOD), catalase (CAT), and total protein (TP) were found in RTF-fed 20% azolla at 28ppt salinity, while the lowest CAT and TP levels occurred in RTF-fed 60% azolla at 5ppt salinity. The highest aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were recorded in the RTF group fed 60% azolla at 5ppt salinity, with the lowest values seen in the group given 20% azolla at 28ppt salinity. RTF fed a 20% azolla diet at 18ppt salinity exhibited the highest lysozyme value, in contrast to the lowest value observed in the RTF group fed the control diet at 18ppt salinity. In conclusion, this study recommends the utilization of azolla at inclusion levels ranging from 20 to 40%, as it has the potential to notably enhance the immune system and elevate the survival rate of RTF.

Ribosomal mutations enable a switch between high fitness and high stress resistance in Listeria monocytogenes.

Multiple stress resistant variants of Listeria monocytogenes with mutations in rpsU encoding ribosomal protein RpsU have previously been isolated after a single exposure to acid stress. These variants, including L. monocytogenes LO28 variant V14 with a complete deletion of the rpsU gene, showed upregulation of the general stress sigma factor Sigma B-mediated stress resistance genes and had a lower maximum specific growth rate than the LO28 WT, signifying a trade-off between stress resistance and fitness. In the current work V14 has been subjected to an experimental evolution regime, selecting for higher fitness in two parallel evolving cultures. This resulted in two evolved variants with WT-like fitness: 14EV1 and 14EV2. Comparative analysis of growth performance, acid and heat stress resistance, in combination with proteomics and RNA-sequencing, indicated that in both lines reversion to WT-like fitness also resulted in WT-like stress sensitivity, due to lack of Sigma B-activated stress defense. Notably, genotyping of 14EV1 and 14EV2 provided evidence for unique point-mutations in the ribosomal rpsB gene causing amino acid substitutions at the same position in RpsB, resulting in RpsB22Arg-His and RpsB22Arg-Ser, respectively. Combined with data obtained with constructed RpsB22Arg-His and RpsB22Arg-Ser mutants in the V14 background, we provide evidence that loss of function of RpsU resulting in the multiple stress resistant and reduced fitness phenotype, can be reversed by single point mutations in rpsB leading to arginine substitutions in RpsB at position 22 into histidine or serine, resulting in a WT-like high fitness and low stress resistance phenotype. This demonstrates the impact of genetic changes in L. monocytogenes' ribosomes on fitness and stress resistance.

Effects of terrestrial animal fats replacing dietary fish oil on the growth performance, antioxidant capacity and lipid metabolism in juvenile Scylla paramamosain

Four experimental diets containing 45% crude protein and 11% crude lipid were formulated by replacing total fish oil (FO) with poultry oil (PO), beef tallow (BT) and lard oil (LO) to evaluate the effects of terrestrial animal fats (TAFs) replacing dietary FO in juvenile green mud crabs (Scylla paramamosain). A total of 120 female juveniles (initial body weight 43.23 ± 0.21 g) was randomly assigned to four diet (three replicates per diet) and stocked into single crab cells (0.23 m × 0.15 m × 0.33 m, width × height × length) with circulating seawater (25–29 °C) for 8 weeks. Compared to FO, crabs fed BT and LO group had about 20% lower weight gain, and significantly lower specific growth rate, feed efficiency and molting ratio, hepatopancreas and muscle lipid, hemolymph total triglyceride contents, and lipase activity, but had approximately 400% higher hepatopancreas aspartate aminotransferase and 100% higher alanine aminotransferase activities. There was no difference in growth performance and feed utilization between PO and other groups. The contents of linoleic acids (18:2n-6) in hepatopancreas and muscle were higher in PO group. TAFs groups had significantly lower docosahexaenoic acids (22:6n-3) and total n-3 polyunsaturated fatty acids contents, as well as lower elongase of very long-chain fatty acids 4, acyl-CoA oxidase 3 and fatty acid transport protein 4 mRNA levels. BT and LO groups had lower mRNA levels of delta-6 fatty acyl desaturase, sterol regulatory element binding protein-1, fatty acid synthase, 6-phosphogluconate dehydrogenase and acetyl-CoA carboxylase. Therefore, dietary BT and LO could reduce the health status and lipid content via decreasing lipase activity, upregulating fatty acid β-oxidation, downregulating lipogenesis and inhibiting the transporting and metabolizing of long chain polyunsaturated fatty acids, thus decrease the growth performance of mud crab. Moreover, PO could be a potential FO substitute for juvenile S. paramamosain.

Response of Bacillus velezensis 83 to interaction with Colletotrichum gloeosporioides resembles a Greek phalanx-style formation: a stress resistant phenotype with antibiosis capacity

Plant growth-promoting rhizobacteria, such as Bacillus spp., establish beneficial associations with plants and may inhibit the growth of phytopathogenic fungi. However, these bacteria are subject to multiple biotic stimuli from their competitors, causing stress and modifying their development. This work is a study of an in vitro interaction between two model microorganisms of socioeconomic relevance, using population dynamics and transcriptomic approaches. Co-cultures of Bacillus velezensis 83 with the phytopathogenic fungus Colletotrichum gloeosporioides 09 were performed to evaluate the metabolic response of the bacteria under conditions of non-nutritional limitation. The bacterial response was associated with the induction of a stress-resistant phenotype, characterized by a lower specific growth rate, but with antimicrobial production capacity. About 12% of co-cultured B. velezensis 83 coding sequences were differentially expressed, including the up-regulation of the general stress response (sigB regulon), and the down-regulation of alternative carbon sources catabolism (glucose preference). Defense strategies in B. velezensis are a determining factor in order to preserve the long-term viability of its population. Mostly, the presence of the fungus does not affect the expression of antibiosis genes, except for those corresponding to surfactin/bacillomycin D production. Indeed, the up-regulation of antibiosis genes expression is associated with bacterial growth, regardless of the presence of the fungus. This behavior in B. velezensis 83 resembles the strategy used by the classical Greek phalanx formation: by sacrificing growth rate and metabolic versatility, resources can be redistributed to defense (stress resistant phenotype) while maintaining the attack (antibiosis capacity). The presented results are the first characterization of the molecular phenotype at the transcriptome level of a biological control agent under biotic stress caused by a phytopathogen without nutrient limitation.

Electromagnetic fields effects on microbial growth in cocoa fermentation: A controlled experimental approach using established growth models

Understanding the effects of electromagnetic fields is crucial in the fermentation of cocoa beans, since through precise control of fermentation conditions the sensory and nutritional properties of cocoa beans could be improved. This study aimed to evaluate the effect of oscillating magnetic fields (OMF) on the kinetic growth of the core microbial communities of the Collections Castro Naranjal (CCN 51) cocoa bean. The data was obtained by three different models: Gompertz, Baranyi, and Logistic. The cocoa beans were subjected to different OMF strengths ranging from 0 mT to 80 mT for 1 h using the Helmholtz coil electromagnetic device. The viable microbial populations of lactic acid bacteria (LAB), acetic acid bacteria (AAB), and yeast (Y) were quantified using the colony-forming unit (CFU) counting method. The logistic model appropriately described the growth of LAB and Y under magnetic field exposure. Whereas the Baranyi model was suitable for describing AAB growth. The microbial populations in cocoa beans exposed to magnetic fields showed lower (maximum specific growth rate (μmax), values than untreated controls, with AAB exhibiting the highest average growth rate value at 5 mT and Y having the lowest average maximum growth rate value at 80 mT. The lower maximum specific growth rates and longer lag phases when exposed to magnetic fields compared to controls demonstrate the influence of magnetic fields on microbial growth kinetics.

Specific Growth Rate (SGR) in Different Stages of Tilapia (Oreochromis niloticus) Production Cycle in Cemented Tank Based Semi-Intensive Aquaculture System

Traditional assessment of specific growth rate (SGR) using the data of the beginning and the end of aquaculture production cycle, avoiding intermediary data, is criticized as misleading way by the scholars. However, by knowing SGR in different stages of fish growth, the utilization of feed by fish can be well known. The study was conducted with aim to assess SGR of Tilapia in six concrete tanks for 90 days from 8th May to 10th August, 2017. Tilapia (Oreochromis niloticus) fry was released at the rate of 4 fry per tank equivalent to the stocking density of 160 fishes/decimal as of the semi-intensive aquaculture system. Sinking and floating feeds were used for feeding the fish in T1 and T2, respectively with three replications for each treatment. During the experimental period, feed was given at the rate of 20%, 15% and 10% of the body weight in 1st, 2nd and 3rd month, respectively. Moreover, aeration facilities were installed for 24 hours using air stone aerator. The weight of fish was recorded using digital balance in 3 days interval to measure SGR. The water quality parameters i.e., temperature and dissolved oxygen (DO) were recorded twice daily. The weight gains of fish were 49.90±2.40 g and 63.12±4.97g for T1 and T2, respectively. The mean percent weight gain of Tilapia was higher in T2 (747±0.00 g) than T1 (253.51±0.00 g). Feed conversion ratio (FCR) in T1 and T2 were 1.70±0.07 and 2.53±0.20, respectively. Considering the data at the beginning and the end of the production cycle, the SGR (% per day) of Tilapia in T1 and T2 were 6.27±3.27 and 6.26±3.83, respectively. The SGR for floating feed was higher at the initial stage of production cycle and lower in the later stages. For sinking feed, SGR was almost static from the beginning to the end. The higher FCR in T2 correlated with the lower SGR in the later stage of the culture period. This confirmed that farmers using floating feed with pre-determined amount of feeding ration, waste the expensive feed and money. Higher total production was obtained in T2 (830.96 g) than T1 (610 g) with 100% survival in both treatments. Therefore, determining SGR in a specific interval, at least 15 days interval, might be the efficient feeding practice of Tilapia farmers.

From urine to food and oxygen: effects of high and low NH4+:NO3- ratio on lettuce cultivated in a gas-tight hydroponic facility.

In situ production of food, water and oxygen is essential for long-duration human space missions. Higher plants represent a key element in Bioregenerative Life Support Systems (BLSS), where crop cultivation can be based on water and nutrients recovered from waste and wastewater. Human urine exemplifies an important waste stream with potential to provide crops with nitrogen (N) and other nutrients. Dynamic waste composition and treatment processes may result in mineralized fractions with varying ammonium (NH4 +) to nitrate (NO3 -) ratios. In this study, lettuce was cultivated in the unique ESA MELiSSA Plant Characterization Unit, an advanced, gas-tight hydroponic research facility offering controlled environment and continuous monitoring of atmospheric gas composition. To evaluate biological and system effects of nutrient solution NH4 +:NO3 - ratio, two crop tests were run with different NH4 + to total N ratio (NH4 +:N) and elevated concentrations of Na+ and Cl- in line with a urine recycling scenario. Plants cultivated at 0.5 mol·mol-1 NH4 +:N (HiNH4 +) achieved 50% lower shoot biomass compared to those cultivated at 0.1 mol·mol-1 NH4 +:N (LoNH4 +), accompanied by higher shoot dry weight content and lower harvest index. Analyses of projected leaf area over time indicated that the reduced biomass observed at harvest could be attributed to a lower specific growth rate during the close-to-exponential growth phase. The HiNH4 + crop produced 40% less O2 over the full cultivation period. However, normalization of the results indicated a marginal increase in O2 production per time and per projected leaf area for the HiNH4 + crop during the exponential growth phase, in line with a higher shoot chlorophyll content. Mineral analysis demonstrated that the biomass content of NH4 + and NO3 - varied in line with the nutrient solution composition. The ratio of consumed NH4 + to consumed N was higher than the NH4 +:N ratio of the nutrient solution for both crop tests, resulting in decreasing NH4 +:N ratios in the nutrient solution over time. The results provide enhanced insight for design of waste processes and crop cultivation to optimize overall BLSS efficiency and hold valuable potential for improved resource utilization also in terrestrial food production systems.

Comparison between batch aerobic biodegradation of paracetamol and glucose with open mixed microbial cultures: Experimental data and kinetic modelling

Biodegradation of man-made chemicals (xenobiotics) in biological wastewater treatment processes is essential to avoid the accumulation of these substances with negative effects on the environment and on human health. This study investigated the aerobic biodegradation of paracetamol as sole carbon and energy source and compared it to a model biogenic substrate (glucose). Batch experiments with unacclimated open mixed cultures from soil were carried out with glucose or paracetamol in a range of concentrations (100–2000 mg/L), measuring the rate of substrate removal, the acclimation time, the oxygen consumption and the COD (chemical oxygen demand) removal. The experimental data were used for kinetic modelling, using several different models based on the Monod kinetics with modifications for inhibition or for acclimation. Paracetamol was biodegraded as sole carbon and energy source at all concentrations (90–97 % COD removal), with slower degradation rate and longer acclimation time than for glucose. From the COD balance, a slightly higher production of microorganisms per unit of substrate COD was calculated for paracetamol than for glucose. The kinetic modelling of the experimental data achieved a good fit with the simple Monod model, but with different parameters for each substrate concentration. Combined fitting of all the experiments with the same set of parameters was attempted, and overall the best fitting was observed with a new model that includes an empirical time constant for acclimation. Compared to glucose, microbial growth on paracetamol was characterised by lower maximum specific growth rate, slightly higher growth yield and higher time constant for acclimation.

Analysis of the effects of specific growth rate of Lactococcus lactis MG1363 on aerobic metabolism and its application to high-density culture

Lactic acid bacteria (LAB) are known to produce a large amount of lactate when cultured under non-aerated conditions, which inhibits their growth at high concentrations. Our previous studies have shown that LAB can be cultured without lactate production under aerated conditions at a low specific growth rate. In this study, we investigated the effects of specific growth rate on cell yield and the specific production rates of metabolites in aerated fed-batch cultures of Lactococcus lactis MG1363. The results showed that lactate and acetoin production could be suppressed at specific growth rates below 0.2 h-1, whereas acetate production was the highest at a specific growth rate of 0.2 h-1. When LAB was cultured at a specific growth rate of 0.25 h-1 with the addition of 5mg/L heme to assist ATP production by respiration, lactate and acetate production was suppressed, and cell concentration reached 19g-dry-cell/L (5.6× 10ˆ10cfu/mL) with a high cell yield of 0.42 ± 0.02g-dry-cell/g-glucose.

Effect of Insect Meals on the Growth Efficiency, Survival and Total Carotenoid Content of an Ornamental Fish Xiphophorus maculatus (Gunther, 1866)

To evaluate the effects of three non-conventional insects (cricket, grasshopper and mealworm) and commercial diet (control) on growth, survival and total carotenoid content of ornamental fish, platy (Xiphophorus maculatus), a feeding trial was conducted in Zoology laboratory, Vidyasagar College, West Bengal, India, between November 2021 and May 2022. A total of 250 platy juveniles (0.04±0.002 gm) were stocked in 12 glass aquariums with 20 fishes for each experimental feed set. Each experimental diet was made per triplicate. The growth efficiency parameters of platy fish in terms of weight gain percentage, specific growth rate (SGR), feed conversion ratio (FCR) were measured at the end of the study period. Protein content in percent is significantly higher in mealworm (46±0.58) and then in grasshopper (42.50±0.29). Final weight of fishes was significantly higher in mealworm fed sets (2.134gm±0.008) and lower in commercial meal fed sets (0.827gm±0.003). The lowest FCR was found in commercial diet (0.458±0.002) and best FCR values was found in cricket diet (0.280±0.001). Higher value of SGR was obtained in mealworm fed sets (2.209±0.002) and lower SGR was in commercial diet (1.683±0.002). Mean survival percentage was 90% in mealworm diet and lowest survival value was 55% at commercial diet. Carotenoid content in fish body was significantly higher in mealworm diet (9.23μg/g±0.071), while lowest was observed in commercial diet (0.47μg/g±0.001). Present study shows that insect diets were better than commercial diet, but mealworm diet was better to increase survival and carotenoid content in X. maculatus.

Delignified porous wood as biofilm support for 1,4-dioxane-degrading bacterial consortium

ABSTRACT Delignified porous wood samples were used as carriers for biofilm formation of a bacterial consortium with the ability to degrade 1,4-dioxane (DX). The delignification treatment of the natural wood resulted in higher porosity, formation of macropores, increase in surface roughness and hydrophilicity of the treated wood pieces. These superior properties of two types of treated carriers (respectively, A and B) compared to the untreated wood resulted in 2.19 ± 0.52- and 2.66 ± 0.23-fold higher growth of biofilm. Moreover, analysis of the fatty acid profiles indicated an increase in proportion of the saturated fatty acids during the biofilm formation, characterising an enhancement in rigidity and hydrophobicity of the biofilms. DX initial concentration of 100 mg/L was completely degraded (detection limit 0.01 mg/L) in 24 and 32 h using the treated A and B woods, while only 25.84 ± 5.95% was removed after 32 h using the untreated wood. However, fitting the DX biodegradation data to the Monod model showed a lower maximum specific growth rate for biofilm (0.0276 ± 0.0018 1/h) versus planktonic (0.0382 ± 0.0024 1/h), because of gradual accumulation of inactive cells in the biofilm. Findings of this study can contribute to the knowledge of biofilm formation regarding the physical/chemical properties of biofilm carriers and be helpful to the ongoing research on bioremediation of DX.

Tragacanth Gum and Linseed Gum as Adhesives Improved the Survival, Digestive Function, Antioxidant Enzyme Activities, and Immunity in Large Yellow Croaker (Larimichthys crocea) Larvae

A 30-day feeding experiment was designed to investigate the effects of different adhesives on survival, growth performance, digestive enzyme activities, antioxidant capacity, and inflammation response of large yellow croaker (Larimichthys crocea) larvae (initial weight 8.40 ± 0.18 mg). Four iso-nitrogenous (55% crude protein) and iso-lipidic (22% crude lipid) microbound diets (MBD) were formulated to contain 2% sodium alginate (SA), 2% tragacanth gum (TG), 2% linseed gum (LG), and 2% poloxamer (PX), respectively. Results showed that larvae fed with TG and LG diets had significantly higher survival rate than the larvae fed with SA and PX ( P &lt; 0.05 ). Larvae fed with the PX diet had lower final weight and specific growth rate than the other groups ( P &lt; 0.05 ). Larvae fed with TG diet had significant higher activities of lipase in pancreatic segments and trypsin in intestinal segments than the larvae fed with the PX ( P &lt; 0.05 ). Meanwhile, the lipase activities of larvae fed with LG was significantly higher in intestinal segments than those fed with SA and PX diets ( P &lt; 0.05 ). Larvae fed with TG and LG diets had significantly higher activities of AKP in brush border membranes than larvae fed with SA and PX diets ( P &lt; 0.05 ). Moreover, the mRNA expression of pcna and zo-1 increased, respectively, in larvae fed TG and LG diets compared with the other groups ( P &lt; 0.05 ). Larvae fed with LG and TG diets had significantly higher activities of SOD and T-AOC than those fed with PX diet ( P &lt; 0.05 ). The content of GSH increased significantly in larvae fed with SA, TG, and LG diets compared with PX treatment ( P &lt; 0.05 ). The activities of iNOS significantly increased in larvae fed with TG and LG diets compared to other groups ( P &lt; 0.05 ). Meanwhile, the mRNA expression of il-10 significantly increased in TG and LG groups ( P &lt; 0.05 ). In conclusion, results of the study demonstrated that TG and LG can be used as feed binders for microdiets with positive effects on survival, activities of digestive enzymes, antioxidant capacity, and inflammatory response. However, PX inhibited the survival and growth, and further study is needed to determine the suitable usage and dosage.

Effects of stocking density on juvenile Amphioctopus fangsiao (Mollusca: Cephalopodasca: Cephalopoda): Survival, growth, behavior, stress tolerance and biochemical response

Stocking density determines the welfare, growth performance, and even survival of aquatic organisms in aquaculture. However, how stocking density affects cephalopods are still unclear. Here we selected Amphioctopus fangsiao, a promising cephalopod for mariculture, to examine the effect of stocking density on survival, growth, physiology and behavior. Juvenile A. fangsiao (≈ two months post-hatch, 2.41 g ± 0.03) were reared for 21 days under different stocking density groups: 30, 45, 60 and 75 individual/m2 (ind./m2) (G1, G2, G3 and G4, respectively). Subsequently, the growth performance, aggressive acts, survival rate, stress response, oxidative stress and glucolipid metabolism were analyzed. This study showed that the high stocking density had a negative impact on growth performance. A. fangsiao reared in G3 and G4 had a significantly lower final body weight, weight gain and specific growth rate than those reared in G1 and G2 (p < .05), and hepatosomatic index in different treatment groups have a similar trend of difference (p < .05). Increased stocking density also caused more fights of A. fangsiao, resulting in a high mortality rate for farmed individuals. The individual numbers of released ink after touch and the recovery time of the breathing rate after air emersion showed that the low stocking density lowered the basal stress level and reduced the recovery time after acute stress of juvenile A. fangsiao. In addition, this study demonstrated that high stocking density has caused oxidative stress and lipid disturbance of A. fangsiao. There were significant differences in reactive oxygen species (ROS), lipid peroxidation's level (MDA content), the activities of superoxide dismutase (SOD) and catalase (CAT), pyruvic acid level (Pyr), total cholesterol level (T-CHO) and triglyceride (TG) between the highest density group (G4) and the lowest density group (G1). Overall, high stocking density (G3 and G4) had a negative effect on reared A. fangsiao. However, there were no significant differences between G1 and G2. Therefore, to improve the welfare of reared A. fangsiao and maximize the economic benefits for producers, juveniles are recommended to rear at a medium density (about 45 ind./m2).

Aqua-Ento-Ponics: Effect of Insect Meal on the Development of Sea Bass, Dicentrarchus labrax, in Co-Culture with Lettuce

The aim of this study is to investigate the effect of 10 and 20% replacement of fishmeal (FM dietary group) with the superworm Zophobas morio larvae meal (ZM10 and ZM20 dietary groups) on the growth performance of sea bass (Dicentrarchus labrax) and lettuce plants (Lactuca sativa) reared in aquaponics. Ninety juvenile sea bass with an average body weight of 21.55 g/individual were placed in aquaponic fish tanks, together with 24 lettuce plants with an average initial height of 8.90 cm/plant and an average number of leaves of 5.75/plant over a 45-day trial period. At the end of that period, all feeding groups exhibited high survival. In fact, ΖΜ10 and ZM20 groups showed similar fish weight gain and specific growth rate (SGR) (p &gt; 0.05), but significantly lower SGR (p &lt; 0.05) than the FM group. Nevertheless, final fish body weight and length were similar (p &gt; 0.05) for all feeding groups. No plant mortality was observed during the 45-day study period. All three aquaponic systems resulted in similar leaf fresh weight, as well as fresh and dry aerial biomass. At the end of the experimental period, plants in the third system showed higher fresh leaf weight, total weight of fresh leaves, total dry aerial biomass, and total produced biomass compared to the other two systems. The results of the present study show that fish fed with the ZM10 diet had higher weight gain (WG) than fish fed with the ZM20 diet, while the SGRs for ZM10 and ZM20 were similar. Both ZM10 and ZM20 diets result in efficient lettuce production. This study also provides data that enlighten the feasibility of integrating insect meals as fish feeds for aquaponics which helps towards the development of an ento-aquaponic approach.

Different responses of grass carp (Ctenopharyngodon idellus) and black carp (Mylopharngodon piceus) to low-protein diets and subsequent recovery

An 8-week growth trial was designed to evaluate the effects of low-protein diets and subsequent recovery on grass carp (Ctenopharyngodon idellus) and black carp (Mylopharngodon piceus) in order to compare the compensatory growth of the two species with different feeding habits. During the restricted period (weeks 1–4), grass carp were fed three kinds of isoenergetic and isolipid diets containing 32% (C, Control), 27% (LEP), and 22% (LP) protein individually, and black carp were fed diets containing 37% (C, Control), 32% (LEP) and 27% (LP) protein individually. In the recovery period (weeks 5–8), all fish were fed the control diets individually. The results showed that the protein restriction led to significantly lower feed conversion efficiency (FCE) and specific growth rate (SGR) for two species. In the recovery period, test group grass carp had similar protein retention efficiency (PRE) and FCE to the control group and had significantly lower final body weights (FBW), succinate dehydrogenase (SDH), significantly higher lactate dehydrogenase (LDH), and aspartate aminotransferase (AST) than the control group. The test group black carp had significantly higher PRE and FCE than the control group, and the LEP group had similar FBW, LDH, AST, and alanine aminotransferase (ALT) to the control group and had significantly lower pyruvate kinase (PK) and SDH. The study reveals that grass carp increase gluconeogenesis and fail to increase feed utilization efficiency significantly, thus failing to obtain compensatory growth. Black carp decrease the carbohydrate catabolism and tricarboxylic acid (TCA) cycle, increase feed utilization efficiency significantly and get compensatory growth in the LEP group. Black carp have better compensatory growth capacity than grass carp, and the different capacities may be related to the different nutrient utilization strategies of the two species.

Entropy and Efficiency of Growth in Marine Fish Species of the Arctic

The mechanisms of the energy exchange processes in fish inhabiting high-latitude regions of Arctic were investigated on the basis of our native experimental data and literature knowledge. It is shown that energy consumption per unit of growth becomes more sparing when they grow slower (low specific growth rate). In this case, the growth process of fish at lower temperatures becomes more and more efficient, and they can grow with minimal energy expenditure. At low temperatures, internal processes slow down and waste accumulates more slowly, which leads to the release of less excess heat generated by metabolic processes and daily activities. In poikilothermic animals, this strategy of using low-entropic energy and "dumping" high-entropic heat at low temperatures is very effective.